1. Field of the Invention
This invention is related to semiconductor substrate positioning mechanism inside a semiconductor device manufacturing system.
2. Description of the Related Art
In the processing of semiconductor substrates, the substrates are at various times placed inside a process chamber where the substrates are subjected to different processing parameters. For example, within an etching process chamber, a semiconductor wafer is placed on a semiconductor support element, such as a chuck assembly, which can serve as a lower electrode. Positioned above the chuck is an upper electrode assembly. The chuck assembly and the upper electrode assembly generate a plasma used, for example, to etch the semiconductor wafer placed on the chuck assembly.
In such an etching process chamber, the semiconductor wafer should be positioned at a certain distance from the upper electrode assembly. To achieve that operation, the chuck assembly, on which the semiconductor wafer is mounted, is moved up and down within the process chamber by a drive system to a desired height below the upper electrode assembly. For example, an operator of a semiconductor processing equipment can set a desired height of a semiconductor wafer within a process chamber by adjusting the extension of drive screws to a desired extension. Movement of the chuck assembly contacts tip ends of the drive screws and thus stops the chuck a desired height within the semiconductor processing chamber. As known in the art, various sensors and feedback systems can be employed to monitor the height of the chuck within the processing chamber to ensure that the chuck supports the semiconductor wafer at the desired height.
Thus, prior art positioning devices can involve chuck assembly movement utilizing multiple lead screw assemblies or pneumatic assemblies. These types of mechanisms typically utilize stop mechanisms along with associated sensors and feedback devices to stop the chuck assembly at a desired position within the semiconductor processing equipment.
For example, pneumatic systems such as described by Eason Jr. et al, in U.S. Pat. No. 6,334,398, the entire contents of which are incorporated by reference, have been used with stops to position a semiconductor support element inside a semiconductor processing equipment, as shown in FIG. 3. FIG. 3 shows a chuck 121 on which a semiconductor wafer is secured. The chuck 121 in turn is supported by a cylinder 122 which moves up and down to pass through an upper support bracket 127 and a lower support bracket 125. The cylinder 122 also includes a lower base 126 attached thereto to move with the cylinder 122.
To ensure that the chuck 121 is at an appropriate height within a processing chamber, the lower base 126 includes three stop screws 124. The stop screws 124 may be adjusted to different heights. Moreover, the device includes a rotatable ring 132 having stop surfaces 133 and 134 configured with different heights, which may be aligned with the stop screws 124. When the cylinder 122 is moved upward, the stop screws 124 will abut against either surfaces 133, surfaces 134 or a bottom of the lower support bracket 125 to stop the cylinder 122 at an appropriate position. As a result the chuck 121 stops at an appropriate height within the processing chamber. An operator of semiconductor equipment may adjust the positioning of the ring 132 and or stop screws 124 to adjust the position at which the chuck 121 stops within the processing chamber.
While prior art chuck height adjustment systems such as shown in FIG. 3 allow adjustment of the chuck assembly to different heights, the adjustment components, such as rotatable ring 132, are typically large and complex, thereby generally requiring a moving device such as a cylinder and associated control circuitry to provide accurate and repeatable movement. Moreover, the complexity of prior art adjustment systems makes it difficult to retrofit such systems into existing processing chambers. In addition, known adjustment systems are generally limited to a small number of adjustment positions. For example, the mechanism of FIG. 3 provides only 3 different heights that can be achieved for a given setting of the stop screws. Finally, the prior art adjustment systems generally use metal hard stops that may wear or damage parts after repeated contact.